U.S.: Tests show mustard gas traces in ISIS attack

August 21, 2015 / 12:58 PM
/ CBS/AP

WASHINGTON -- A senior U.S. military officer says preliminary tests show traces of the chemical agent sulfur mustard on mortars that Islamic State of Iraq and Syria (ISIS) militants used to attack Kurdish forces in Iraq.

U.S. Brig. Gen. Kevin Killea, chief of staff for the military operations in Iraq and Syria, says the field testing is not conclusive, so final tests are underway to get the full make-up of the chemicals on the fragments.

U.S. officials have been looking into reports that ISIS militants used the chemical weapon mustard gas in the August 11 attack in Makhmour. Similar reports surfaced in July.

Killea told Pentagon reporters on Friday that Kurdish forces brought the mortar fragments to U.S. forces for testing, so there may be questions about the chain of custody of the evidence.

Last week, a senior Defense Department official told CBS News that the reports of mustard gas use were "credible" but the Pentagon later dialed back that report.

A German Defense Ministry statement last week said some 60 Kurdish fighters suffered from breathing difficulties as a result of the attack. It said none of the German soldiers training the Kurds in the area 37 miles southwest of the city of Irbil were hurt or in danger.

Flash Points: What chemical weapons mean for the fight against ISIS

CBS News senior national security analyst Juan Zarate said that the attack was significant but not a "game-changer."

"It's not a game-changer with respect to the threat in general," Zarate said. "We've known that ISIS has not only maintained territory and momentum but has been advancing in terms of its weaponry, and there have been concerns that ISIS has gotten its hands on chemical weapons, so that concern is not new.

"The fact that it's being confirmed though, that they used it against peshmerga and the U.S. has to confront it, may be a game-changer, and that may be the real problem here: The reality that ISIS is continuing to expand and adapt and to adapt in ways that are incredibly dangerous."